First Draft: Static Single Assignment

[jmh530]

On Monday, 17 November 2025 at 01:08:58 UTC, Walter Bright wrote:
> On 11/16/2025 2:08 PM, Nick Treleaven wrote:
>> On Sunday, 16 November 2025 at 01:50:16 UTC, Walter Bright 
>> wrote:
>>> https://github.com/WalterBright/documents/blob/master/final.md
>> 
>> ```d
>> final int f = 3;
>> f = 4; // error, f is final
>> int* p = &f; // error, cannot make mutable reference to final 
>> variable
>> const int* pc = &f; // ok
>> ```
>> 
>> So I assume `typeof(&f)` would be `const int*`?
>
> `final` is not part of the type system. So typeof(&f) would be 
> `int*`.

Would it make sense to make final/head-const part of the type 
system? Other than that it makes it more difficult to implement.

I recall there were a lot of discussions in the past about 
converting something that is head const to tail const, or maybe 
the reverse. I think the issue was that it was built-in for D's 
arrays, but you can't easily do that if you have your own 
aggregate. There seemed to have been some desire to have that 
functionality in the language.